This invention generally relates to valve mounting assemblies for aerosol containers, said mounting assemblies being commonly referred to as xe2x80x9cmounting cups.xe2x80x9d More particularly, this invention relates to an improved gasket for the mounting cup, i.e., the gasket that forms the seal between the perimetal rim of the mounting cup and the bead of the aerosol container, wherein the sleeve gasket is folded over on itself to provide a double thickness of gasket material disposed within the channel portion of the mounting cup. Also, the invention relates to a method and apparatus for forming the folded-over gasket after the gasket material has been disposed on the mounting cup.
Aerosol containers are widely used to package a variety of fluid materials, both liquid and powdered particulate products. Typically, the product and a propellant are confined within the container, at above atmospheric pressure, and the product is released from the container by manually opening a dispensing valve to cause the pressure within the container to deliver the product through the valve and connecting conduits to a discharge orifice.
The dispensing valve, crimped to a mounting cup having a sealing gasket, is normally mounted in a top opening of the container, which opening is defined by a component commonly referred to as the xe2x80x9cbeadxe2x80x9d of the container opening. The mounting cup includes a central pedestal portion for crimping the dispensing valve, a profile portion extending outward from the pedestal portion, which profile portion merges into an upwardly extending body portion, the body portion emerging into a channel portion terminating in a skirt portion, which channel is configured to receive the bead portion of the container opening. The sealing gasket normally is disposed within the channel portion and in many gasket configurations extends downward along a part of the body portion. After the sealing gasket is disposed onto the mounting cup, the cup is positioned onto the container and the cup is clinched to the container. The clinching operation is well-known to those skilled in the aerosol container art.
In an aerosol container, an effective seal between the mounting cup and the container bead is obviously critical. This seal is accomplished through the sealing gasket, which must prevent the loss of pressure (propellant) through the interface between the container bead and mounting cup.
Various types of sealing gaskets are known in the art. One common type of gasket comprises a conventional flat rubber gasket that is placed inside the channel of the mounting cup. Gaskets of this type are typically manufactured by extruding, molding and vulcanizing the compounded rubber mixture onto rods and then cutting or slicing off thin, annular sections of the extruded and vulcanized product (tube). These gaskets are often referred to as cut or flat gaskets. Cut gaskets are relatively expensive to manufacture. It is very difficult to control precisely the radial dimensions of the tubes from which the cut gaskets are made, the tubes having varying dimensions and being out of round. Consequently, the outer cylindrical surfaces of these tubes are usually machined to the desired dimensions, said machining adding considerable cost to the gasket manufacture.
Another type of gasket comprises a relatively thin sleeve of elastomeric material that is mounted on the body portion of the mounting cup and then advanced along said body so that the gasket extends ultimately into a limited portion of the annular channel of the mounting cup as well as downward along the body portion beyond the annular clinch zone. When the mounting cup is mounted and then clinched onto the aerosol container, the sealing gasket is forced into a sealing engagement with both the channel of the mounting cup and the bead of the container. Typically, these gaskets are forced into a sealing engagement with the mounting cup along only a relatively small circumferential portion of the gasket at positions referred to as the 5 o""clock and 11 o""clock positions. Due to their shape, gaskets of this type are often referred to as sleeve gaskets.
Sleeve gaskets are manufactured by advancing a tube of gasket material onto the body of the mounting cup and then cutting or slicing off annular sections of the tube. The axial heights of sleeve gaskets are substantially greater than the axial heights of cut gasket. Sleeve gaskets are much less expensive to make and assemble to the mounting cup than cut gaskets. When making sleeve gaskets, it is not necessary to machine the outside cylindrical surface of the extruded tubes of gasket material. Moreover, a tubular sleeve gasket may be assembled to the mounting cup more easily than assembling a cut gasket to the mounting cup.
The sealing gasket may also be formed by a liquid material containing water or solvent that is deposited on the annular channel and body portion of the mounting cup. The solvent or water evaporates during curing and the remaining material produces a resilient sealing material in the mounting cup channel. Forming the gasket from a liquid material also is a comparatively expensive procedure requiring multiple production steps including the use of curing ovens or other means to dry and cure the gasket material. Moreover, means must be provided for rotating the mounting cup beneath and relative to a metering apparatus that dispenses carefully determined amounts of a gasket forming composition. These gaskets are commonly referred to as xe2x80x9cflowed-inxe2x80x9d gaskets. The xe2x80x9cflowed-inxe2x80x9d gasket system is disfavored due to environmental concerns.
Thus, the above described types of gaskets, as well as others that may be used, have both advantages and disadvantages. Both cut and sleeve gaskets generally produce excellent sealing results. Cut gaskets have seen widespread commercial use for a longer period of time than sleeve gaskets. When using sleeve gaskets on filling and clinching equipment previously used with flat or cut gaskets, a time consuming adjustment must be made to the clinching tool. Often, a clinching line will be required to accommodate both flat and sleeve gaskets, depending on the gasket specifications of the valved container being clinched. To avoid having to make the clinching tool adjustment, with its consequent down-time, there has been a tendency, particularly in Europe, to stay with flat or cut gaskets, even though such gaskets are more costly.
In the past, an attempt has been made to overcome the disadvantages of a cut gasket by converting a specially dimensioned sleeve-type gasket into a cut-type gasket. This attempt is described in U.S. patent application Ser. No. 08/384,736, filed on Feb. 3, 1995. A disadvantage of utilizing the aforementioned sleeve/cut-type gasket is that the apparatus used to manufacture the sleeve-type gasket is designed to handle tubing having a thickness on the order of 0.014xe2x80x3. Cut gaskets generally are 0.040xe2x80x3 thick, and to manufacture sleeve-type gasket material for conversion into a cut-type gasket of 0.040xe2x80x3 or more requires a significant retooling.
U.S. patent application Ser. No. 08/512,533, describes a gasketed mounting cup comprising a sleeve-type gasket that has been folded onto itself to provide a gasket having a double thickness, i.e., a thickness approaching the thickness of a cut gasket; said application further describing that the segments of the folded-over gasket are of uneven length, the segment distal to the under surface of the mounting cup being considerably longer than the segment contiguous to the mounting cup surface. In U.S. patent application Ser. No. 09/037,669, filed on Mar. 10, 1998, there is described a gasketed mounting cup comprising a folded-over gasket for a mounting cup having a flat-bottomed channel portion, wherein the gasket segment distal to the mounting cup has a greater length than the gasket segment contiguous to the mounting cup, this varying length of the segments of the gasket being in combination with a reduction in the width of the channel portion of the mounting cup as compared to conventionally sized mounting cups. Use of a non-conventionally sized mounting cup adds a cost factor.
An object of this invention is to provide an improved gasketed mounting cup for aerosol containers, an improved method for assembling the gasket to the mounting cup and novel apparatus for forming the gasket of this invention.
Another object of the present invention is to provide a mounting cup for an aerosol container with a sealing gasket that has the manufacturing cost advantages of a sleeve gasket and the advantages of the thickness of a cut gasket in the clinching operation of the aerosol container.
In its broadest aspect, as an article of manufacture, the improved gasketed mounting cup of this invention comprises a mounting cup having a curvilinear channel portion in which is disposed a sleeve-type gasket having plural segments of dissimilar length folded onto each other, which segments are joined at a continuous fold line and positioned such that, when the gasket is ultimately clinched into position in the channel portion of the mounting cup, the fold line is radially outward from the portion of the gasket contiguous to the body of the mounting cup and the length of the folded-over gasket segment distal to the channel portion of the mounting cup is of a greater length than the other segment, however, the longer segment should not have any significant portion, and preferably no portion, thereof contacting the mounting cup during positioning into the channel portion of the mounting cup. If the length of the gasket segment distal to the mounting cup is of a length that a portion thereof abuts or rides against the body portion of the mounting cup, there is an opportunity for the gasket to be wedged against the body portion between the body portion and the bead of the container when the bead attempts to advance the folded-over gasket along the body and into the channel of the mounting cup with the result that the folded-over gasket will not advance into the channel to the desired position and will, thus, produce an imperfect gasketed mounting cup. This is particularly a problem with mounting cups having a curvilinear-shaped channel portion.
The thickness of the individual segments of the gasket will interplay in determining the permissible percent of length increase of the longest segment. The larger the thickness of each segment of the folded-over gasket, the greater is the permitted percent increase of the longer segment of the gasket over the shorter segment. This is for the reason that a shorter segment of greater thickness increases the distance of the longer segment from the surface of the body portion.
In a preferred form of the gasket, the sleeve thickness is 0.022 inches and the length of the gasket segment distal to the mounting cup should be no greater than one hundred twenty-five (125%) percent of the gasket segment contiguous to the mounting cup.
In a still more preferred form of the mounting cup, the fold-over sleeve gasket is an ultra low density polyethylene with an added thermoplastic elastomer.
In the broadest aspect of the method of this invention, the gasket of this invention is formed by advancing the gasket material in the form of a sleeve along the body portion and into the channel portion of the mounting cup and thereat advancing a tool that creates an annular line of compressive force against the gasket thereby causing a continuous fold line in the gasket with the result that the portion of the gasket distal to the body portion of the mounting cup folds over on the other portion of the gasket material, wherein the advancing tool that creates the continuous fold line in the gasket strikes at a point along the length of the sleeve gasket to form folded-over segments of the gasket having the desired relative lengths.
The novel apparatus of this invention comprises a punch that is mounted in a reciprocating manner; the punch advancing the sleeve gasket into the channel portion whereat it advances against the gasket. The working part of the punch has a downwardly and inwardly directed taper on its outer surface, as well as flats on the outer surface that reduce the contact area of the folded-over gasket and the outer surface of the punch and, thereby, preclude dislodgement of the folded-over gasket from the mounting cup during withdrawal of the punch. More detail on the punch is presented hereafter.
Further to the method of forming the gasketed mounting cup of this invention, after the outer portion of the gasket has been folded onto the inner portion, at the point where the gasket is partially in the channel, the gasket is then urged further into the channel portion of the mounting cup. In the mounting cup of the invention, the channel portion of the mounting cup is curvilinear in shape, the gasket is initially disposed upright along the body portion of the mounting cup and slightly into the channel portion contiguous to the body portion of the cup with the free edges of the gasket contiguous to the body portion of the mounting cup. The insertion of the bead of the container into the channel portion advances the gasket to conform to and against the curvilinear shape of the channel portion of the mounting cup.
To dispose the sleeve gasket on the mounting cup prior to forming the fold-over gasket, the sleeve gasket of this invention is initially positioned onto the body portion of the mounting cup. The sleeve gasket is then cut from an extruded tube of gasket material. After cutting, the sleeve gasket is then partially advanced along the body portion of the mounting cup and then further advanced into the annular channel thereof in two separate steps, whereat a compression force against the sleeve gasket results in forming plural segments of the sleeve gasket which fold over onto each other. The apparatus and process for carrying out the steps shown in FIGS. 3A and 3B hereof are described in U.S. patent application Ser. No. 08/512,533, filed on Aug. 8, 1995, the disclosure of which application is hereby incorporated by reference.
Several attempts have been made to simulate cut gaskets for aerosol mounting cups through provision of a folded-over sleeve gasket. In the case of mounting cups having a curvilinear-shaped channel portion, particularly, where the container is aluminum and industry-known eyelashing problem in the bead of the container is present, these attempts have met with imperfect results due to inconsistent positioning of the gasket from its ultimate desired position due to compressibility characteristics in the material of composition of the gasket and in the relative lengths of the segments of the fold-ever gasket. It has been here discovered that with curvilinear-shaped channels, an excessively longer outer gasket segment may provide a contiguous contact to the body portion of the mounting cup for a length sufficient to be clamped between the outside wall of the body of the mounting cup and the bead of the container thereby preventing proper advancing of the gasket to its desired position in the channel. This is a problem peculiar to curvilinear-shaped channels.
Further benefits and advantages of the invention will become apparent from a consideration of the following detailed description given with reference to the accompanying drawings which specify and show preferred embodiment of the invention.